Surveying Lecture 3
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Transcript of Surveying Lecture 3
8/7/2019 Surveying Lecture 3
http://slidepdf.com/reader/full/surveying-lecture-3 1/19
CE-419 : Principles of RemoteSensing
Subashisa Dutta
Department of Civil Engineering
IIT Guwahati
Lecture –6: Physical basis of SignaturesRef: George Joseph, Fundamentals of Remote Sensing
Contact email for lecture ppts : [email protected]
8/7/2019 Surveying Lecture 3
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SIGNATURE
0.4 0.8 1.2 1.6 2.0 2.4
REFLEC
TANCE
(%)
Wave length (m)
WATER (Shallow/Deep)
VEGETATION
SILTY CLAY SOIL
MUCK SOIL
0
20
40
60
80
Signatures could be inferred through:
• Spectral Variation
• Polarisation Change
• Thermal Inertia
• Temporal Variation
Key to feature identification from space imagery depends on the
characteristic changes in the properties of the EM spectrum
reflected/emitted from the target surface – referred ‘signature’
Signatures are not completely
deterministic; they are statistical in
nature with a mean and dispersion
Radiance (mw/cm2 / str/ m)
0
1000
2000
3000
4000
5000
6000
7000
2.79 3.08 3.37 3.66 3.95 4.24 4.53 4.82
F r e q u e n c y
2S Dutta/CE/IITG8/16/2010
8/7/2019 Surveying Lecture 3
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Sample field vegetation spectralmeasurement
Field Measurements
3S Dutta/CE/IITG8/16/2010
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4S Dutta/CE/IITG8/16/2010
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Reflectance from a leaf
5S Dutta/CE/IITG8/16/2010
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6S Dutta/CE/IITG8/16/2010
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7S Dutta/CE/IITG8/16/2010
8/7/2019 Surveying Lecture 3
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8S Dutta/CE/IITG8/16/2010
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The spectral response for inorganic materials is
distinct from vegetation types.
9S Dutta/CE/IITG8/16/2010
8/7/2019 Surveying Lecture 3
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• Gradual rise in reflectance with increasing
wavelengths.
• Concrete, light-colored and bright, has higher
% refl than dark asphalt.
10S Dutta/CE/IITG8/16/2010
8/7/2019 Surveying Lecture 3
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• Refl for veg. rises
abruptly at ~0.7 µm,
followed by a gradual
drop at about 1.1 µm.
0.3 - 0.5 µm - most veg. types similar in response
0.5 - 0.6 µm moderate variations
0.7 - 0.9 µm - maximum variability
(optimum discrimination)
11S Dutta/CE/IITG8/16/2010
8/7/2019 Surveying Lecture 3
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• 4 spectral curves
• Variations in depths of absorption bands.
12S Dutta/CE/IITG8/16/2010
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13S Dutta/CE/IITG8/16/2010
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Some crops distinguishable by separations in 0.56 to 0.66 µm interval.
14S Dutta/CE/IITG8/16/2010
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15S Dutta/CE/IITG8/16/2010
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Spectral signature for paddy fields
Paddy Field Crop height measurement
Paddy field with water
background
Spectroradiometer
( 350 –
1050 nm)
16S Dutta/CE/IITG8/16/2010
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Temporal variation of spectral signature of paddyfields
Data source : NRDMS Project,
IIT Guwahati 17S Dutta/CE/IITG8/16/2010
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Background effects of vegetation reflectance spectra
• Vegetation cover reflectance : a mixture of reflectance fromthe vegetation, soil ( water) underneath and the shadow.
•
At the low vegetation cover, background reflectance frombare soil dominates
• At the peak vegetation stage, reflectance from vegetation
dominates
• Controlled by direction of the sun rays and view direction
18S Dutta/CE/IITG8/16/2010
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• End of lecture-6
19S Dutta/CE/IITG8/16/2010